Direction of arrival estimation with a vector intensity hydrophone array towed by an autonomous surface vehicle.

Using pressure gradient-based methodology, a compact 33-cm, four-element, tetrahedron-shaped hydrophone array is demonstrated to emulate the low-frequency direction of arrival (DOA) finding performance of a vector sensor. Towed from an autonomous surface vehicle in deep water, near the Kelvin and Atlantis II seamount complexes, this array is capable of determining the horizontal DOA (i.e., bearing) of low-frequency broadband (210-310 Hz) transmissions from bottom-moored sources located at a depth of ∼1100 m and ranges up to 176 km away. Both coherent and incoherent DOA finding methods are presented, producing consistent DOA values for signal-to-noise ratios higher than 11 dB for the selected experimental configuration.